Care & maintenance of septic tanks / wastewater treatment systems

Many factors may contribute to septic/wastewater system failure, including:

  • too much wastewater, especially in surges
  • using chemicals which kill decomposing bacteria in the system e.g. disinfectants, detergents, bleaches (minimal use is recommended)
  • extended periods of rainfall
  • excessive shadowing or compacting of the evapo-transpiration area
  • leaking plumbing which overloads the system
  • tree roots growing into and plugging trenches
  • inadequate disposal area


If you own or rent a house that is not connected to the sewerage system provided by Sydney Water, you will have some type of sewage management system on the property. Any system that stores, treats or disposes of sewage on a site must be maintained in a manner that ensures no impact occurs to public health and the environment . These systems are all classified as on-site sewage management systems and require approval to operate under the Local Government Act 1993. All aerated wastewater treatment systems must be inspected by an approved company every three months to maintain sufficient chlorine in the system and ensure the system is working satisfactorily. Other systems are required to be inspected on a regular basis: High Risk systems must be inspected every year, Medium Risk every two years and Low Risk every three years.  Most septic systems on the island will be High or Medium risk.

The former Pittwater Council introduced compulsory inspections to be carried out by qualified contractors with the relevant paperwork to be completed and forwarded back to Council for approval. Property owners are notified by Council when inspection is due. Follow link to the Northern Beaches Council website for more information.

System maintenance

Septic tanks produce a sludge that collects on the bottom of the tank and a floating scum on the surface of the liquid.

The primary septic tank will require a pump-out every five to ten years, depending on the load. Failure to clean out a tank when required may cause scum to be carried out of the primary tank and into the disposal system.


Research has shown that mosquitoes have a limited range, so if you are have a lot of mosquitoes, it may be because of inadequate screening or water management in your property or in neighbouring properties.

Do your bit to reduce compulsory blood donations and possible infections by screening all inlets and outlets to your tank, including the overflow pipe. Also, have a look around outside and remove any containers that could collect water, such as trays around pot plants.

Cleaning products

Check the labelling on all household cleaning and washing products:

  • The best choice are detergents that are phosphate—free with no boron compounds and low sodium.
  • Extra phosphates and boron damage native plants and encourage excessive weed growth.
  • Salts change the structure of the soil so that it becomes less permeable.

Sodium levels are generally much higher in non-concentrated powders and brands that advertise their ‘softening powers.’